In infinite schedule mode, Cetec ERP determines how many calendar days are required to perform all labor and buffer/queue time for a work order. It then subtracts that total from the ship date to determine the work start date.

This calculation has two major components:

• Labor days (based on an item labor plan’s estimated setup/run time and the hours_per_workday setting)
• Buffer/queue days (based on buffer hours divided by a fixed 24-hour day)

In simple terms:

Total schedule days = labor days + buffer days

The work start date is calculated by subtracting this total from the ship date.

The hours_per_workday setting determines how many hours of labor fit into one labor day.

Example configuration:

7 hours per labor day

So:

7 hours of estimated labor = 1 labor day

14 hours = 2 labor days

3.5 hours = 0.5 labor days

Cetec ERP always rounds labor days up to the next whole day.

Examples:

3.5 ÷ 7 = 0.5 → rounded to 1 labor day

17.3 ÷ 7 = 2.47 → rounded to 3 labor days

This rounding happens before buffer time is added.

Buffer or queue time is always calculated using a 24-hour calendar day, regardless of the hours_per_workday setting.

Example:

82 hours of buffer ÷ 24 = 3.41 buffer days

Buffer days are not rounded. They remain fractional and are added after labor rounding.

Buffer represents waiting time between operations rather than active labor. Because of this, it spans full calendar days rather than labor days.

14 hours ÷ 7 hours/day = 2 labor days.

With no buffer time:

Total schedule requirement = 2 calendar days.

Example:

Ship date: Aug 7

Work start date: Aug 5

3.5 ÷ 7 = 0.5 → rounded to 1 labor day.

Meaning:

With no buffer, work start = ship date.

Any buffer up to 23 hours still keeps the total under 2 days, so the work start date does not move.

Only when the total reaches 2.00 days does the start date move back one day.

Because 3.5 hours of labor rounds to 1 labor day:

1 labor day + X buffer days ≥ 2 days

Solve for X:

X ≥ 1 calendar day → 24 hours

So:

24 hours of buffer → work start moves back one day

48 hours of buffer → work start moves back two days

Example input:

Qty: 1

17.3 hours setup + run

82 hours buffer/queue

hours_per_workday = 7

Step 1 - Convert estimated labor into labor days

17.3 ÷ 7 = 2.47 → rounded up to 3 labor days

Step 2 - Convert buffer hours into buffer days

82 ÷ 24 = 3.41 buffer days

Step 3 - Add them together

3 labor days + 3.41 buffer days = 6.41 calendar days

Step 4 - Subtract from ship date

If ship = Aug 7, work start ≈ Aug 1 (or late July depending on fractional handling).

Operations are planned sequentially, immediately back-to-back.

Unless buffer/queue time is inserted between operations, the next operation begins as soon as the previous one ends, even if that means mid-day.

Example:

Operation 1 = 5 hours

Operation 2 starts immediately after that.

To force the next operation to begin the following day, at least 24 buffer hours must be inserted between the two operations.

This is because buffer is calculated relative to a 24-hour clock, not the labor day.

3.01 hours and 6.99 hours both become 1 full labor day when hours_per_workday = 7.

23 hours buffer = 0.96 days.

This is not enough to push the schedule back to the previous day.

Without buffer between operations, each operation starts immediately after the previous one.

Some users assume buffer respects the 7-hour labor day, but it does not.

Labor uses hours_per_workday.

Buffer always uses a 24-hour day.

You can usually predict scheduling behavior quickly:

1. Divide labor hours by hours_per_workday and round up.
2. Divide buffer hours by 24.
3. Add the two values together.

The total must exceed whole-day boundaries (1, 2, 3…) to push the start date further back.

Infinite schedule mode does not constrain capacity.

It assumes any amount of labor can be done on any given day. The only question is:

How many calendar days are required, and how far should the schedule back up from the ship date?

Finite schedule mode behaves differently, but that is outside the scope of this document.

Cetec ERP converts labor time into rounded labor days, converts buffer time into 24-hour calendar days, adds them together, and subtracts that total from the ship date to determine the work start date in infinite schedule mode.